How to determine the refresh rate for dashboard widgets

From other threads I understand that each dashboard widget has it's own refresh interval and this interval is not configurable by the user.

Is there a method to determine the refresh rate for each widget?

For the Work Item widget I discovered this was 10 minutes, but I would prefer not to sit watching a dashboard for a trend report widget to determine how often it is refreshed. Possibly I could video record the screen to capture the refresh and perform a binary search through the recording, but there are a lot of widgets...  Is there a better way, e.g. a reference document?